"IsLoading" indicator for overlay/splash screen

For a Perspective page- I want to put up a watermarked indicator over the entire window or just some components when a SQL query/data processing script is currently running, so that the user knows the data is still loading.

I vaguely recall an “IsLoading” property on some Vision components. Is there a similar mechanism in Perspective? If not, has anyone achieved this by alternative means?

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